War Attack use the WebGL technology. As result, you web browser do not ask you to instal any plug-in.
The WebGL will be soon the only way to release a game playable in your web browser. But currently the performances is acceptable only with a decent computer.
The web browser vendors (Google Chrome,FireFox, Internet Explorer ect ...) work already hardly to improve the performances and to fixe some bugs that can be present.
We can expect a lot of changes for 2017 in terms of performances and compatibility.
The game is currently in development/Alpha stage, developed by one man and do not represent the final product.
Stay tuned !